IntroductionPaclitaxel is used widely in the treatment of breast cancer. Not all tumors respond to this drug, however, and the characteristics that distinguish resistant tumors from sensitive tumors are not well defined. Activation of the spindle assembly checkpoint is required for paclitaxel-induced cell death. We hypothesized that cyclin-dependent kinase (CDK) 1 activity and CDK2 activity in cancer cells, which reflect the activation state of the spindle assembly checkpoint and the growth state, respectively, predict sensitivity to paclitaxel.MethodsCell viability assays and DNA and chromatin morphology analyses were performed in human breast cancer cell lines to evaluate sensitivity to paclitaxel and the cell cycle response to paclitaxel. We then examined the specific activities of CDK1 and CDK2 in these cell lines and in xenograft models of human breast cancer before and after paclitaxel treatment. Protein expression and kinase activity of CDKs and cyclins were analyzed using a newly developed assay system.ResultsIn the cell lines, biological response to paclitaxel in vitro did not accurately predict sensitivity to paclitaxel in vivo. Among the breast cancer xenograft tumors, however, tumors with significantly increased CDK1 specific activity after paclitaxel treatment were sensitive to paclitaxel in vivo, whereas tumors without such an increase were resistant to paclitaxel in vivo. Baseline CDK2 specific activity was higher in tumors that were sensitive to paclitaxel than in tumors that were resistant to paclitaxel.ConclusionsThe change in CDK1 specific activity of xenograft tumors after paclitaxel treatment and the CDK2 specific activity before paclitaxel treatment are both associated with the drug sensitivity in vivo. Analysis of cyclin-dependent kinase activity in the clinical setting could be a powerful approach for predicting paclitaxel sensitivity.

The detection of circulating tumor cells (CTCs) in peripheral blood is currently an important field of study. Detection of CTCs by the OBP-401 assay (TelomeScan®) has previously been reported to be useful in the diagnosis, prognosis and evaluation of therapeutic efficacy in breast and gastric cancer. The aim of the present study was to evaluate the OBP-401 assay as a novel method of detecting CTCs of small cell lung cancer (SCLC) patients and to evaluate whether CTC count is associated with prognosis. Prospectively, 30 consecutively diagnosed SCLC patients who had commenced chemotherapy or chemoradiotherapy were enrolled as subjects of the current study. Peripheral blood specimens were collected from the SCLC patients prior to and following the initiation of treatment and the viable CTCs were detected in the specimens following incubation with a telomerase-specific, replication-selective, oncolytic adenoviral agent, which was carrying the green fluorescent protein gene. CTCs were detected in 29 patients (96%). The group of 21 patients with a CTC count of <2 cells/7.5 ml prior to treatment (baseline) had a significantly longer median survival time than the group of eight patients with a CTC count of ≥2 cells/7.5 ml prior to treatment (14.8 and 3.9 months, respectively; P=0.007). The results of a multivariate analysis showed that the baseline CTC count was an independent prognostic factor for survival time (hazard ratio, 3.91; P=0.026). Among the patients that achieved a partial response to treatment, patients who had a CTC count of <2 cells/7.5 ml following two cycles of chemotherapy tended to have a longer median progression-free survival compared with patients who had a CTC count of ≥2 cell/7.5 ml (8.3 and 3.8 months, respectively; P=0.07). Therefore, CTCs may be detected via OBP-401 assay in SCLC patients and the CTC count prior to treatment appears to be a strong prognostic factor.

BackgroundThe identification of circulating tumour cells (CTCs) in peripheral blood is a useful approach to estimate prognosis, monitor disease progression, and measure treatment effects in various malignancies. However, clinical relevance of CTCs is controversial. We attempted to detect viable CTCs in the peripheral blood of gastric cancer patients using a telomerase-specific viral agent.MethodsWe took a 7.5-ml blood sample from 65 treatment-negative gastric cancer patients before surgery and 10 healthy volunteers. We detected viable CTCs in the blood samples after incubating them with a telomerase-specific, replication-selective, oncolytic adenoviral agent carrying the green fluorescent protein (GFP) gene (OBP-401). GFP-positive CTCs were defined as having a diameter of at least 7.735 μm; this threshold was determined by receiver operating characteristic curve analysis. GFP-positive cells were counted under a fluorescence microscope.ResultsThere was a significant difference in overall survival among the patients with 0–4 and those with ≥5 GFP-positive CTCs in the stage I–IV disease group and stage II–IV advanced disease group. The number of GFP-positive CTCs was not related to cancer stage. Among the pathological findings, the number of GFP-positive CTCs was only significantly related to venous invasion, although there were trends towards more GFP-positive CTCs with disease progression (tumour depth, lymph node metastasis, distant metastasis, lymphatic invasion, and histological type).ConclusionsThere was a significant relationship between the number of GFP-positive CTCs and overall survival in the patients with gastric cancer. The detection of CTCs using OBP-401 may be useful for prognostic evaluation.Trial registrationUniversity Hospital Medical Information Network in Japan, UMIN000002018.

Background:There are no established biomarkers to identify tumour recurrence in stage II colon cancer. As shown previously, the enzymatic activity of the cyclin-dependent kinases 1 and 2 (CDK1 and CDK2) predicts outcome in breast cancer. Therefore, we investigated whether CDK activity identifies tumour recurrence in colon cancer.Methods:In all, 254 patients with completely resected (R0) UICC stage II colon cancer were analysed retrospectively from two independent cohorts from Munich (Germany) and Leiden (Netherlands). None of the patients received adjuvant treatment. Development of distant metastasis was observed in 27 patients (median follow-up: 86 months). Protein expression and activity of CDKs were measured on fresh-frozen tumour samples.Results:Specific activity (SA) of CDK1 (CDK1SA), but not CDK2, significantly predicted distant metastasis (concordance index=0.69, 95% confidence interval (CI): 0.55–0.79, P=0.036). Cutoff derivation by maximum log-rank statistics yielded a threshold of CDK1SA at 11 (SA units, P=0.029). Accordingly, 59% of patients were classified as high-risk (CDK1SA ⩾11). Cox proportional hazard analysis revealed CDK1SA as independent prognostic variable (hazard ratio=6.2, 95% CI: 1.44–26.9, P=0.012). Moreover, CKD1SA was significantly elevated in microsatellite-stable tumours.Conclusion:Specific activity of CDK1 is a promising biomarker for metastasis risk in stage II colon cancer.

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Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) catalyzes the isomerization of PGH 2 , a common precursor of various prostanoids, to produce PGD 2 , an endogenous somnogen and nociceptive modulator, in the brain. L-PGDS is a member of the lipocalin superfamily and binds lipophilic substances, such as retinoids and bile pigments, suggesting that L-PGDS is a dual functional protein acting as a PGD 2 -synthesizing enzyme and a transporter for lipophilic ligands. In this study we determined by NMR the three-dimensional structure of recombinant mouse L-PGDS with the catalytic residue Cys-65. The structure of L-PGDS exhibited the typical lipocalin fold, consisting of an eight-stranded, antiparallel ␤-barrel and a long ␣-helix associated with the outer surface of the barrel. The interior of the barrel formed a hydrophobic cavity opening to the upper end of the barrel, the size of which was larger than those of other lipocalins, and the cavity contained two pockets. Molecular docking studies, based on the result of NMR titration experiments with retinoic acid and PGH 2 analog, revealed that PGH 2 almost fully occupied the hydrophilic pocket 1, in which Cys-65 was located and all-trans-retinoic acid occupied the hydrophobic pocket 2, in which amino acid residues important for retinoid binding in other lipocalins were well conserved. Mutational and kinetic studies provide the direct evidence for the PGH 2 binding mode. These results indicated that the two binding sites for PGH 2 and retinoic acid in the large cavity of L-PGDS were responsible for the broad ligand specificity of L-PGDS and the non-competitive inhibition of L-PGDS activity by retinoic acid. Lipocalin-type prostaglandin (PG)2 D synthase (L-PGDS, prostaglandin H 2 D-isomerase, EC 5.3.99.2) (1-3) catalyzes the isomerization of the 9,11-endoperoxide group of PGH 2 , a common precursor of various prostanoids, to produce PGD 2 with 9-hydroxy and 11-keto groups, an endogenous somnogen (4) and a modulator of pain responses (5), in the presence of sulfhydryl compounds. L-PGDS is the only enzyme among members of the lipocalin gene family (6) that is composed of a group of lipid-transporter proteins, such as retinol-binding protein, ␤-lactoglobulin, major urinary protein, aphorodisin (6 -8), epididymal retinoic acid-binding protein (9), and tear lipocalin (10). L-PGDS has three Cys residues, Cys-65, Cys-89, and Cys-186, conserved among all species. Two of these Cys residues, Cys-89 and Cys-186, form a disulfide bridge, which is highly conserved among most, but not all lipocalins (6). This disulfide bridge can be removed without a significant loss of the enzymatic activity. On the other hand, Cys-65 is unique to L-PGDS, as it has never been found in other lipocalins. Moreover, the replacement of Cys-65 with Ser/Ala by site-directed mutagenesis led to complete loss of the catalytic activity of the recombinant rat (11), human, mouse, chicken (12), and bull and frog (13) enzymes, indicating that the Cys-65 residue is the key residue for the reaction catalyzed by L-P...

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Let's twist again: A cation–π interaction between Trp and Arg is designed at the interface between two α helices of a coiled‐coil structure and stabilizes the structure more than Glu and Lys ion‐pair interactions. Two or three Trp–Arg sets form an extended array of interactions (see picture) and increase the melting temperature of the peptide.